1. Field of the Invention
The present invention relates to glass processing equipment with dynamic production control. Specifically, the invention relates to a dynamic tempering furnace optimizer for tempering furnace of a glass cutting line, a glass production line having dynamic production control and a method of controlling a glass production line tempering furnace.
2. Background Information
Glass processing equipment including glass cutting lines that have glass cutting tables, are well-known in the art, such as those sold by the assignee of the present invention, Billco Manufacturing, Inc. The central piece of equipment in the glass cutting line is the glass cutting table, examples of which are described in U.S. Pat. Nos. 5,791,971, 6,463,762 and 6,810,784, which are incorporated herein by reference. The glass cutting table is designed to cut generally rectangular glass sheets into a plurality of individual glass work pieces for subsequent manufacturing. The typical glass cutting line will also include a sheet feeding device upstream of the glass cutting table for feeding the glass sheets to be cut to the glass cutting table. The sheet feeding device may be in the form of an air float table to which individual glass sheets to be cut are fed, such as from a storage rack, and then aligned prior to forwarding to the glass cutting table.
A known glass cutting line arrangement will also include a sorting device downstream of the glass cutting table where the cut glass sheets are individually sorted by the specific glass work pieces into storage racks, generally called harp racks. A harp rack is provided with a number of slots, such as 100, for receiving the individual cut glass work pieces. The sorting device may be formed as an air float table with a plurality of adjacent harp racks. The harp racks are moved to the next part of the assembly operation.
Existing glass cutting lines typically utilize a production control system designed to minimize scrap. Previously, a specific cutting schedule for a production run, or single batch, was prepared in advance by the control system. The production run essentially corresponded to the number of harp racks and associated slots at the sorting station. Basically, older optimization programs were used to determine the optimal cutting schedule for filling the slots of the harp racks with the desired glass work pieces.
The cutting schedule essentially refers to the collection of layouts of the individual glass work pieces on all the glass sheets to be cut for the production run or batch. Following the batch production run, the filled harp racks were moved to the next location in the manufacturing process. The older optimization systems were limited by several problems. First, each system was limited by the number of available slots in the available harp racks. In general, the greater the number of slots the greater the yield since the optimizing program will have a greater number of pieces to select from to maximize product yield. Second, the harp racks generally could not be moved until the entire production run is completed, including the re-cuts at the end of the batch process. Third, the existing last sheet problem increased yield loss, even with re-cuts incorporated into the last sheet. Additionally, the existing older systems do not easily accommodate special pieces not accounted for in the production run.
The problems with older optimizers on cutting lines were addressed by Billco Manufacturing with the development of the Batch Ban® glass equipment optimization product. This system provided a dynamic cutting line control system that includes an optimizer coupled to the controller of the glass cutting table optimizing the glass work piece layout on the individual sheets of glass. The optimizer includes a dynamically adjustable bias or biasing feature for favoring individual cut glass work pieces assigned to a leading storage position such as in a harp rack, whereby the bias will tend to position and cut the glass work pieces assigned to the leading position or harp rack on leading sheets to completely fill the leading harp rack in a minimum time. The control system further accommodates removal of a filled leading harp rack from the glass cutting line, with the system designating a new leading harp rack for the optimizer, which then dynamically adjusts the bias and associated cutting scheduling. This system provides an optimization system that operates “on the fly” allowing the previous batch type systems to be continuous or semi-continuous processes. The Batch Ban® product is described, in part in U.S. Pat. Nos. 7,043,323 and 6,879,873 and these patents are incorporated herein by reference.
The patent application that issued as U.S. Pat. Nos. 7,043,323, discussed above, published as U.S. Publication No. 2005-0182506 on Aug. 18, 2005. U.S. Publication No. 2005-0182506 was cited by the examiner in parent international Patent Application Ser. No. PCT/US2008/074127 as a “document defining the general state of the art which is not considered to be of particular relevance” to the claims of that application. Similarly, patent application that issued as U.S. Pat. Nos. 6,879,873, discussed above, published as U.S. Publication No. 2003-0226433 on Dec. 11, 2003. U.S. Publication No. 2003-0226433 was cited by the examiner in parent international Patent Application Ser. No. PCT/US2008/074127 as a “document defining the general state of the art which is not considered to be of particular relevance” to the claims of that application.
The Batch Ban® product can also be described as overlapping batches that are dynamically optimized “on the fly”. The Batch Ban® product is not limited to the pieces designated for the storage locations currently at the cutter break out table. As noted in U.S. Pat. No. 6,879,873, it is also known to have one harp rack, or storage location, that is designated for “rare” pieces, or pieces that are not in the production cycle for some time, and this is called the rare rack. The rare rack acts as a storage location for pieces until needed, which is until the rack that they are associated with is moved into position on the break out table.
The commercial implementation of the Batch Ban® product has resulted in large commercial savings where implemented. There is a need to expand the applications for the dynamic optimization system of the Batch Ban® type product.
A separate glass processing step for many glass types is tempering through a tempering oven. Conventional tempering ovens will have a loading zone where the glass work pieces are loaded onto a moving bed of the furnace, a heating zone, a cooling zone and an unloading zone. A conveyer generally operates in a continuous fashion moving pieces through the tempering furnace.
It is known for workers loading a tempering furnace to have a specified layout prepared by a tempering furnace optimizer, such as, for example the BEDMATE™ product sold by PMC Software. The workers at the unloading zone will typically be provided a layout and identification of the work pieces as they exit the furnace so they can be sorted and racked accordingly. The input and output assistance is generally through graphical displays at each end of the furnace.
PMC Software attempted to increase productivity and throughput by trying to more fully automate processing from Cutting to Tempering. They provided a revised direct feed system in which cut glass is conveyed directly from the glass cutting line to the tempering furnace, eliminating the need to rack glass as it travels between these work centers in order to reduce the possibility of scratching or breaking caused by excessive handling. The direct feed system from PMC Software allows the user to process tempered requirements without the need to sort and rack cut glass. Operators still build tempered batch loads by viewing a TV monitor display and placing each lite within a batch on the load bed as shown on the display. In this direct feed automated process, orders are first scheduled for production and then optimized in batch type optimizer. Using the breakout sequence of the optimized layouts, a tempering optimizer portion of the system then determines the best orientation of the pieces to meet roll distortion requirements and to optimize the load bed. Once a production schedule is optimized, it is available to the cutting machine operator via the local area network. When an optimized layout has been cut and conveyed to the breakout table, the Breakout Display will automatically display that layout to demonstrate which lite is to be loaded first onto the conveyor feeding the load bed of the tempering furnace, as each lite is identified by a sequential loading number. To insure the orientation of each lite placed on the conveyor is correct, it is loaded base first. A sequence number is also displayed on the tempering furnace Load Display showing where each lite is to be placed within a tempering load. As a load exits the tempering furnace, the Off-Load Display identifies each lite within that load to assist off-load personnel in either packing or racking tempered lites.
It is well known that glass work pieces can be and are damaged at every stage of the production cycle. It is often considered that the more handling steps that are incurred with a work piece the greater the likelihood of damage to the work piece. In addition to scratching due to handling, miss-breaks, work pieces can be irreparably damaged in the tempering furnace itself. Regardless of the cause, the damaged pieces must be replaced. Traditionally, in batch production, these replacement pieces are run following the completion of the current batch. This final replacement batch can significantly hinder the production as it may result in exceptionally low yields as there can be very limited glass types in this final batch process.
U.S. Pat. No. 6,810,784 was cited by the examiner in parent international Patent Application Ser. No. PCT/US2008/074127 as a “document defining the general state of the art which is not considered to be of particular relevance” to the claims of that application. U.S. Pat. No. 6,810,784 discloses a glass transporting and locating system for a glass cutting table with a bridge extending across the glass cutting table which is movable along the length of the glass cutting table. A glass work-piece feeding table is positioned adjacent the glass cutting table and adapted to support a glass work-piece to be fed to the glass cutting table. At least one vacuum chuck is carried by the bridge at a position which can overlap a glass work-piece supported on the glass work-piece feeding table when the bridge is at one end of the glass cutting table. The system includes a device for aligning the glass work-piece which is supported on the glass work-piece feeding table. The alignment device may include a retractable stop on the bridge or on the glass work-piece feeding table. The retractable stop on the bridge may also be used for advancing finished work-pieces off of the glass cutting table. The glass work-piece transporting and locating system is adapted to be easily retrofitted to existing glass cutting tables. U.S. Pat. No. 6,810,784 is discussed herein for completeness in light of its citation in the search report of the parent application, but this patent does not directly relate to the glass production lines of the present invention.
It is an object of the present invention to improve the efficiencies of glass production lines incorporating a tempering furnace.